[tutumarks]

 How many moles of sulfamic acid were used each run? Show your calculation. [1 mark]
(Note: 25mL of the stock solution was used for each run).       
 
n = 0.00640
mm = 0.621 g
MM = 97.094

Stock solution = 25 mL

My answer for moles in weight of 0.621 g of Sulfamic acid is 0.00640. I am confused on how to find the moles is my stock solutions.

[sjb]

A full procedure might help - how for instance did you get the figures you have shown?